DESCRIPTION Our objectives are to better understand the role of Helicobacter pylori infection on the risk of gastric cancer, and its interaction with genetic susceptibility, high intake of salt or salty food, smoking, green tea drinking, and family history of cancer in the development of gastric cancer. We will make use of available data and blood sample from a population-based case-control study in order to establish the synergic effects between H. Pylori, GST M1 and T1, smoking, other environmental and familial factors. We choose Yangzhong County, one of areas with the highest incidence and mortality of gastric cancer in the world, as a study base. With a collaborative effort, all 733 study subjects (133 incident cases with gastric cancer, 166 cases with chronic gastritis, and 434 population controls) were interviewed by a standard questionnaire in Yangzhong County, and blood specimens were available in 539 subjects. The epidemiologic data and blood specimens were stored at our Cancer Center. We propose that H. pylori infection may be involved in the early stage of gastric carcinogenesis and this process may be modulated by genetic susceptibility, smoking, and other nutritional and environmental and familial factors. We will measure serum IgG antibody against H. pylori infection in order to evaluate the relationships between H. pylori infection and chronic gastritis as well as stomach cancer. We will evaluate the association between the risk of gastric cancer and genetic susceptibility, environmental and familial factors. We will assess interaction effects between H. pylori infection, genetic susceptibility, environmental and familial factors on the risk of chronic gastritis and stomach cancer. We only request funding for H. pylori infection detection, DNA extraction, and GST M1 and T1 measurement for these subjects. The results may be useful in the future planning and designing an appropriate intervention study in this high risk area which can reduce the incidence of gastric cancer in the high risk population.